Mesozoic basin evolution of the East China Sea Shelf and tectonic system transition in Southeast China

The East China Sea Shelf Basin (ECSSB) is located on the south‐eastern edge of the Eurasian Plate. The tectono‐evolution and dynamic mechanism of the ECSSB are related to the collision of the Pacific Plate with the Eurasian Plate, and the remote pushing effect of the Indo‐Australian Plate remains a hot topic of debate. Based on the latest survey data, this paper mainly focuses on the evolution of the Mesozoic basin in the East China Sea Shelf by means of assessing the regional tectonic background, conducting structural physical simulation experiments, and applying balanced geological section recovery technology to discuss the processes of dynamic transition in Southeast China. Our data suggest that the ECSSB experienced an evolutionary sequence involving the pre‐Late Triassic passive continental margin; the Late Triassic–Middle Jurassic active continental margin extrusion‐depression; the extrusional stress from the low‐angle subduction of the Izanaki Plate under the Eurasian Plate; the late Early Cretaceous to Late Cretaceous active continental marginal extension faulted basin, during which the extensional stress originated from the lithospheric thinning and palaeoenvironment resulting from the subduction of the Palaeo‐Pacific Plate under the Eurasian Plate; and the Palaeogene back‐arc extension faulted sags. The transition time from the E‐W‐trending Palaeo‐Tethys tectonic system to the NE‐trending Palaeo‐Pacific tectonic system in Southeast China occurred at the end of the Middle Triassic. The low‐angle subduction and withdrawal of subduction of the Palaeo‐Pacific Plate probably represented the deep geological processes of the Mesozoic in Southeast China.


2011;
. There is still great controversy on the Mesozoic intracontinental deformation mechanisms, coccoliths, cyanobacteria, and sponge spicule nannofossils. The intermagmatic activities, and dynamic processes in Southeast China. A large number of studies have shown that the Mesozoic South China Block has undergone structural transition from the E-W-trending Tethys system to the NE-trending West Pacific system Li & Li, 2007;Shu et al., 2004;Sun, Ding, & Hu, 2007;Wu, Zhang, Chen, parallel & Wu, 2000;Zhang et al., 2013;. The ECSSB is located at the south-eastern edge of the South China Block, and the dynamics of its tectonic evolution are closely related to the direction of the movement of the Pacific Plate. It is key area to explore the transformation of the tectonic deformation system in the South China Block. This paper is mainly focused on the Mesozoic basin evolution processes of the ECSSB, and explores the geodynamic transformation processes based on previous related work through regional tectonic background analysis, structural physical simulation experiments, structural analysis, and balanced geological section recovery technology, combined with the latest geological survey and results.

| GEOLOGICAL SETTING
The ECSSB is located in a major area of convergence and lithospheric thinning among the Indo-Australian Plate, the Pacific Plate, and the Eurasian Plate. It is located at the centre of global convergence Maruyama, Isozaki, Kimura, & Terabayashi, 1997). The east and west sides of the East China Sea are separately related to the evolution of the western Pacific tectonic domain and Tethys tectonic domain, which are important parts of the western Pacific continental margin system ( Figure 1).
Regionally, the ECSSB is located at the south-eastern edge of the South China Block. Its basement is an extension of the Cathaysian Block on the East China Sea Continental Shelf Zhang, Zhang, & Tang, 2014).
In the Mesozoic, the basement strata, the depression strata, and the faulted strata are divided from bottom to top in the ECSSB.
Each stratum is bounded by regional unconformity. The basal structural strata refers to the various rocks and structural deformations before the formation of the basin. It mainly includes Proterozoic-Palaeozoic metamorphic rock series and is a metamorphic crystalline basement from the west-Early Indosinian period of the South China Sea with multiple layers in a longitudinal direction (Li & Zhu, 1992;Yang & Li, 2003). Guangdong, Fujian, Southwest Japan, to the Okinawa Islands (Yang, Li, & Dai, 2011;Yang, Li, Gong, & Yang, 2015). Examining material from drilling in the East China Sea, the lower section is grey, black mudstone and grey sandstone sandwiching a thin coal seam; the bottom (not in) for the thick sandstone with thin mudstone; the upper is grey sandstone, brown and tan mudstone, and light greygrey mudstone in unequal interlayers (Figure 2), containing nal reflected energy is medium-weak, and its continuity is normalpoor on seismic profiles. The profiles show a relatively uniform lithological depositional environment with a set of parallel-like dense reflections (200 ms) at the bottom, and the internal composition is like to parallel-messy from blank reflections ( Figure 3) (Chen & Hu, 2017), it is shown that the sedimentary-geotectonic background in the Cretaceous is mainly that of an island arc transition zone (island arc or continental arc; Figure 4).

| Trace elements used to discriminate the tectonic setting of the source area
The trace elements in terrigenous clastic rock, especially including La, Th, Zr, and Sc have greater stability (Bhatia, 1983). In the process of weathering, transportation, and deposition, it is seldom affected by

| Balanced geological section recovery technology
The restoration of balanced geologic section is used to test the rationality of the interpreted seismic section (Gibbs, 1983). By restoring the section to its original state, the processes of stretching and

| Structural physical simulation methods and materials
The structural physical simulation experiment is used to reproduce the structural deformation process and study the deformation behaviour of the structure. A large number of simulation experiments show that the process of structural deformation is mainly controlled by geometric conditions and has little relationship with rock mechanical properties and stress magnitude (Braun, Batt, Scott, Mcqueen, & Beasley, 1994;McClay & White, 1995). The boundary conditions and deformation models of the physical simulation are usually obtained according to the actual deformation mode of the study area. Through the study of the compositional characteristics of the research section using similar conditions to select experimental materials, the deformation characteristics and evolution processes of the model with increasing corresponding variables can be studied (Zhou, Qi, & Tong, 1999). Although the method for determining similar conditions is derived from the mathematical equations of rock deformation (Table 1), there are still many uncertainties about the mechanical properties of rock under long-term high temperature and low strain rate deformation conditions. Therefore, the current relative conditions are summarized by experimental experience. The general similarity conditions are used as a general reference in the selection of experimental materials.
Finally, the structural morphological changes of the model are approximated to the actual structural phenomena as the main criteria.
According to the principle of material similarity (Table 1), soft materials such as clay, petrolatum, silica gel, and raw rubber in the experimental materials can be appropriately formulated to obtain the corresponding experimental parameters, and are the preferred soft materials that meet similar conditions. The tensile strength of loose quartz sand is close to zero, and its deformation characteristics are in line with the Coulomb failure criterion. It is the same as the deformation characteristics of shallow rock in the crust. Loose quartz sand is a material that mimics the deformation of shallow crust. The density of materials such as honey and syrup is similar to that of the asthenosphere, and they are common materials for the simulation of the asthenosphere (Faccenna et al., 1996;Faccenna, Giardini, Davy, & Argentieri, 1999). According to the principle of material similarity, the simulation experiment in this paper uses loose, dry quartz sand to represent sandstone, conglomerate, and other rock formations with strong deformability to verify the previous generation of mantle plume genetic models and rifting genetic models in the East China Sea Basin.
Balloon expansion and magmatic upper arch models were used for simulation-based research. Central magmatic intrusion, fissure-type magmatic intrusion, and superimposed simulation experiments with extension were also conducted. By comparison, the simulation experiment on the uplift boundary double extrusion and superimposed bilateral extension (Figure 7) is closest to the present structural deformation characteristics of the basin (Figures 8 and 9).
On the right side of the model seen in Figure 7, the right subduction boundary is made according to the similarity of the Ryukyu trench pattern (scale: 1.0 × 10 −6 , model 1 cm represents an actual 10 km). A plastic mat is placed on the lower part of the steel plate on the right side of the model, and its shape is similar to that of the right side.
Three protrusions are made of foam on the left side of the model,
Their disagreement focused on whether the tectonic setting of the basin during the Mesozoic was an extruding or a stretching environment. According to plate tectonics, a trench-arc-basin system can be   (Gao et al., 2009). The nature of the crust still retains the characteristics of continental crust. However, the thickness of the crust is only between 15 and 24 km (Jin & Yu, 1987), which shows that the evolution of the basin is already at the highest stage of continental crust and fracture (Zhou, Liao, Jin, & Jia, 2001). This is

| Extrusional depression of the active continental margin in the Late Triassic-Middle Jurassic
In   (Figure 10b).
Due to the differences in the study area, research objectives, and research methods, there are differences in the start-up time for inferred tectonic transformation. Ren (1984) and Ren, Chen, Niu, Liu, and Liu (1990) (Ma, 1992). However, there is no evidence that there was a subduction zone in the Indosinian in the eastern part of South China. Therefore, it was inferred that this may be a passive continental margin facing the Palaeo-Pacific (Pan-Ocean).
In the Early Triassic, the eastern margin of the Palaeo-Tethys extended eastward into southern China, and most of Guangdong, Guangxi, Southwest Yunnan, and Southeast Yunnan developed marine  (Li, 2008 Plate active continental margin (Li, Santosh, et al., 2012;Yang et al., 2012 the expansion period of the continental margin. The regional stress field changed from extrusion to stretching (Niu, 2015). According to subduction-forming 80-90 Ma blue schronosphere belts in Taiwan and Japan (Ma, 1992), indicating that there is a subduction active continental margin along the East Asian continent in the early Late Cretaceous. Through the restoration of its structural features (Sengor & Natalin, 1996), it was thought that the continental margin was still an Andean-type active continental margin (James & Sacks, 1999).
However, due to the combined effect of Pacific Plate subduction and western Indo-Eurasian Plate collision, the continental margin was in the background of the right-handed shear stretch for the East Asian continent and brought about a series of pull-basins that were mainly controlled by NE-trending strike-slip faults along the continental margin and the inland region in the Late Cretaceous to the Eocene.
The Cenozoic basin evolution has obvious stages under the control of the regional stress field. During the Palaeocene-Eocene Period, the direction of Pacific Plate movement shifted from WNW-trending to NNW-trending, subjecting the entire East China Sea Shelf to a single main shear stress field. This led to a series of verrucous faulted depressions in the basin and two regional tectonic events that are Before the Middle Jurassic, the subduction was low angle. After the Early Cretaceous, the subduction plates were turned from low angle to high angle, and the subduction relented.